/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.fnexecution.control;



import com.bff.gaia.unified.vendor.guava.com.google.common.collect.Maps;



import java.time.Duration;

import java.util.Map;

import java.util.concurrent.CompletableFuture;

import java.util.concurrent.ExecutionException;

import java.util.concurrent.TimeUnit;

import java.util.concurrent.TimeoutException;



/**

 * A {@link ControlClientPool} backed by a client map. It is expected that a given client id will be

 * requested at most once.

 */

public class MapControlClientPool implements ControlClientPool {



  /** Creates a {@link MapControlClientPool}. */

  public static MapControlClientPool create() {

    return new MapControlClientPool();

  }



  private final Map<String, CompletableFuture<InstructionRequestHandler>> clients =

      Maps.newConcurrentMap();



  private MapControlClientPool() {}



  @Override

  public Source getSource() {

    return this::getClient;

  }



  @Override

  public Sink getSink() {

    return this::putClient;

  }



  private void putClient(String workerId, InstructionRequestHandler client) {

    CompletableFuture<InstructionRequestHandler> future =

        clients.computeIfAbsent(workerId, MapControlClientPool::createClientFuture);

    boolean success = future.complete(client);

    if (!success) {

      throw new IllegalStateException(

          String.format("Control client for worker id %s failed to compete", workerId));

    }

  }



  private InstructionRequestHandler getClient(String workerId, Duration timeout)

      throws ExecutionException, InterruptedException, TimeoutException {

    CompletableFuture<InstructionRequestHandler> future =

        clients.computeIfAbsent(workerId, MapControlClientPool::createClientFuture);

    // TODO: Wire in health checking of clients so requests don't hang.

    future.get(timeout.getSeconds(), TimeUnit.SECONDS);

    InstructionRequestHandler client = future.get();

    clients.remove(workerId);

    return client;

  }



  private static CompletableFuture<InstructionRequestHandler> createClientFuture(String unused) {

    return new CompletableFuture<>();

  }

}